Glacial Retreat
The earth has seen some 20 odd periods of glaciation in the last 3 million years, interspersed with warmer interglacials. So the temperature of the planet has fluctuated wildly in the past. The difference now is the rate of change. Human induced global warming is causing the average temperature of the earth to rise faster than at any time in its history. One of the most obvious signs of this is the rate at which the majority of the earth√?¬?s glaciers are now retreating. Glaciers tend to be found in mountainous areas, being a keen mountaineer I have seen with my own eyes the rate of retreat of glaciers in France, Switzerland, Austria, Italy, Kenya and the USA. Many of the world√?¬?s glaciers are a vital water resource from summer melting. If they disappear completely, as they inevitably will from many areas, it will lead to huge water shortages.